INTEGRATED REGIONAL CLIMATE
STUDY WITH A FOCUS ON THE
LAND-USE LAND-COVER CHANGE
AND ASSOCIATED CHANGES IN
HYDROLOGICAL CYCLES IN THE
SOUTHEASTERN UNITED STATES
INTEGRATED REGIONAL CLIMATE STUDY WITH A
FOCUS ON THE LAND-USE LAND-COVER CHANGE AND
ASSOCIATED CHANGES IN HYDROLOGICAL CYCLES IN
THE SOUTHEASTERN UNITED STATES
Collaborative, interdisciplinary project initiated under IDS
Roger Pielke Sr. (PI)
Dev Niyogi*
Toshihisa Matsui
Hsin-I Chang
Christian Kummerow
Souleymane Fall
Michael B. Coughenour
Joseph Alfieri
Dept. Atmos. Sci.,
Natural Resources Lab.
Depts. of Agronomy and Earth
and Atmos. Sciences,
Colorado State University
Purdue University
Introduction….
Study LULC/
biospheric
processes in
weather and
climate models
under effect of
different/ multiple
simultaneous
forcings
1700
1900 LCLUC affects regional and global climate
Intensive Crop Land
Mixed Forest Grassland, Agriculture
Reduction in rainforest and moist
deciduous forest from 1981 - 1990
1970
1990
OUTSTANDING SCIENCE QUESTION
How does the change in radiative forcing
associated with the LCLUC and cloud
radiative-precipitation process affect the
terrestrial biogeochemical, the hydrological
cycles, and the surface energy budget?
IDS LCLUC /Hydrology Project Objectives
•Variability in surface latent heat flux (evaporation and
transpiration) and precipitation and hence the regional
hydrological cycle
•Variability due to LCLUC, radiation and cloudprecipitation process, and terrestrial ecosystem
processes
•Examine the individual, as well as the combined
effect
•Investigate the feedbacks under drought and nondrought conditions
•Use detailed process models, in-situ and remotesensed satellite data and products
Coupled Modeling System
-GEMTM and RAMS based
-Several interactive processes
-Surface and satellite data ingestion
-Process based assessment possible
Task 1 Calibration and Evaluation of Biogeochemical
Process in the GEMRAMS Model
•How are regional biogeochemical and water cycles
responding to the variation of radiative forcing?
•What is the effect of the variation in the radiative forcing
on plants and regional landscapes regulated by the soil
moisture anomalies?
Task 1 Calibration and Evaluation of Biogeochemical Process
in the GEMRAMS Model
•Calibration Efforts are detailed in a poster (Matsui
et al.)
•Optimization approach and tests with different datasets
•Modular GEMRAMS code to ingest variable data sources and formats
•Calibration using observations and optimization models
•Testing and evaluation
Focus of this presentation….
•How are regional biogeochemical and water
cycles responding to the variation of radiative
forcing and LULC?
- CLOUDS AND AEROSOLS
AFFECT THE RADIATIVE
FEEDBACK OF THE
ENVIRONMENT
-Majority of the studies have
focused on the ‘temperature
effects’ =>whether clouds and
aerosols cause cooling or
warming effect in the regional
climate.
-In this study we propose that:
Clouds and Aerosols, in
particular, also have a
significant biogeochemical
feedback on the regional
landscapes; this feedback
will change as a function of
LULC; and should be
considered in carbon and
water cycle studies
Diffuse Radiative Feedback over Different
Landscapes
Clouds and Aerosols (haze, smoke…) can change the radiative
forcing.
Total solar radiation = (Diffuse + Direct) solar radiation
For increased Cloud Cover or Increased Aerosol Loading,
Diffuse Component Increases => changes the DDR (Diffuse to Direct
Radiation Ratio)
We hypothesize that:
Increase in DDR will impact the Terrestrial
Water and Carbon Cycle through Transpiration and Photosynthesis
changes
(Transpiration is the most efficient means of water loss from land surface;
Photosynthesis is the dominant mechanism for terrestrial carbon cycle)
Outstanding Questions…
Is the effect of increasing photosynthesis and
transpiration rate observed at leaf and canopy
scale, also valid at field and regional scale?
Will increased DDR and aerosol loading affect
water vapor and CO2 fluxes (at field scale)?
Are the effects of aerosols significant so as to
be included in biogeochemical and land surface
process studies at field and regional scale
Study expected to represent an additional
(biogeochemical) means of quantifying the
impacts of LCLUCs
Approach:
Synthesize field measurement for CO2
and water vapor fluxes over different
landscapes under different environmental
conditions and aerosol loading.
Data :
Need simultaneous observations of CO2 flux, water
vapor flux, radiation (including DDR), and aerosol
loading.



CO2 and water vapor flux and landscape biophysical
information – Ameriflux
Radiation (including DDR) information from Ameriflux or
NOAA Surface Radiation (SURFRAD) sites
Aerosol loading information from NASA Aerosol Robotic
Network (AERONET) and MODIS and IMPROVE AOD
(comparison paper by Matsui et al. 2004; published Nov 2004 –
Geophys. Res. Lett.)
Study sites
Six sites available across the globe that have information
on the required variables for our study (aerosol optical
depth: AOD,diffuse radiation,CO2 flux,and latent heat flux)
Shidler, OK
(grassland
98,99)
Ponca, OK
(wheat 98,99)
Barrow, AK
(grassland 99)
Willow Creek, WI
Lost Creek, WI
(mixed forest,00,01)
Bondville, IL
(agriculture,
C3 / C4, 9802)
Walker Branch, TN
(mixed forest 2000)
Hypothesis to be tested from the
observational analysis :
Increase in the aerosol loading could increase
CO2 and latent heat flux at field scales


This would indicate a more vigorous terrestrial carbon
cycle because of aerosol interactions
This would also indicate potential for changes in the
terrestrial water cycle because of aerosol loading
Data Analysis Flow Chart
Sub-objectives of our first part of the study are:
1. Do DDR changes affect field scale measurements?
2. What is the effect of clouds on DDR and field scale CO2 flux? , and
3. What is the effect of aerosols on field scale CO2 Flux?
Analysis 1
If > 0.6
High Diffuse
If < 0.4
Low Diffuse
Diffuse Fraction
If Smooth
Anaysis 2
Clear
Satellite
Verified
Radiation Flux
If Reduced
If > 0.6
Analysis 3
Cloudy
High Aerosol Loading
Aerosol Loading
If < 0.4
Low Aerosol Loading
Does DDR Change Cause Changes in the CO2
Flux at Field Scale?
Walker Branch Forest Site
-CO2 flux into the vegetation (due
to photosynthesis) increases with
increasing radiation
-For a given radiation, CO2 flux is
larger for higher DDR
Rg-total radiation
Rd-diffuse radiation
negative values indicate CO2 sink
(into the vegetation)
Effect of DDR on field scale CO2 Flux
Does DDR Change
Cause Changes in the
CO2 Flux at Field
Scale?
Yes!
Changes in CO2 flux Normalized for
changes in global Radiation versus
Diffuse Fraction
Increase in DDR
appears to increase
the observed CO2 flux
in the field
measurements.
Do clouds affect CO2 flux at Field Scale?
- Yes, clouds appear to affect field scale CO2 fluxes significantly.
-CO2 flux into the vegetation (due to photosynthesis) is larger for cloudy
conditions
Do Aerosols affect field scale CO2 Flux?
- Increase in AOD (no cloud conditions) causes increase in DDR (diffuse fraction)
- CO2 flux into the vegetation (due to photosynthesis) is larger for higher AOD
conditions
- Aerosol loading appears to cause field scale changes in the CO2 flux
Are these results true for different
landscapes?
Forests
Croplands
Grasslands
For Forests and Croplands, aerosol loading has a positive effect on
CO2 flux, where there shows a CO2 flux source at Grassland sites.
Effects of AOD Wavelength on the
CO2 – aerosol sensitivity
Cropland (Soybean)
-10
CO Flux (micro mol/m2/s)
-15
-20
2
1020
870
-25
670
340
380
500 440
-30
0
0.2
0.4
0.6
Aerosol Optical Depth
0.8
1
Summary for Carbon cycle data analysis:
Increasing aerosols could increase CO2
flux at forest and crop sites; decrease
CO2 flux over grassland sites
There were some differences in the response for
photosynthesis pathway (C3 or C4).
-In general C4 plants appear to be more sensitive.

AOD-carbon sensitivity could be wavelength- dependent for
forest sites, while it is relatively less for croplands.
Do Aerosols affect water vapor flux?
Photosynthesis and transpiration are inter-related.
If aerosols increase photosynthesis rates, what will be the
impact on Transpiration?
Increased transpiration flux could indicate increased vigor
of the water cycle.
Hypothesis to be tested from the
observational analysis:
Increase in aerosol loading will significantly
affect the transpiration rate and hence the
water vapor flux (Latent Heat Flux)
Effect of AOD on water vapor flux (LHF)
over different landscapes.
350
500
450
300
350
300
250
200
150
WB(00)
LC(01)
WC(00)
100
50
400
300
200
100
BV(98)
BV(00)
BV(02)
BV(99)
BV(01)
Ponca(99)
0
-100
0
0.2
0.4
0.6
0.8
Aerosol Optical Depth
Forest site
1
Latent Heat Flux (W/m2)
Latent Heat Flux (W/m2)
La tent Heat Flux (W/m2)
400
0
0.2
0.4
0.6
0.8
Aerosol Optical Depth
Cropland
1
250
200
150
100
50
Shidler 1998(LHF)
Shidler 1999(LHF)
0
-50
1.2
Barrow 1999(LHF)
0
0.1
0.2
0.3
0.4
0.5
0.6
Aerosol Optical Depth
Grassland
Unlike CO2 fluxes, latent heat flux appears to generally
(not always) decrease with increasing Aerosol Optical
Depths for most of the sites
0.7
LHF-Diffuse Radiation relation
(Normalized for Global Radiation Changes)
BV 2000
400
400
350
Latent Heat Flux (W/m2)
Latent Heat Flux (W/m2)
BV 1999
450
350
300
250
200
150
100
-0.2
300
250
200
150
100
0
0.2
0.4
0.6
0.8
Rd/Total Radiation(Rg)
Corn
1
50
0
0.2
0.4
0.6
0.8
Rd/Rg
Soybean
Latent Heat Flux decreases with increasing Diffuse
Radiation Ratio
1
Why is there no consistent relation between AOD and LHF?
LHF-Diffuse Radiation relation
The scatter in the data
shows… Diffuse Radiation
change alone, is not the
driver for latent heat flux
changes!
BV LHF vs Diffuse Radiation
Latent Heat Flux (W/m2)
500
400
300
200
100
(Note that, transpiration
may still correlate with
diffuse radiation as plant
studies have shown!!)
LHF(98)
LHF(99)
LHF(00)
LHF(01)
0
-50
0
50
100
150
200
250
Diffuse Radiation (W/m2)
LHF = transpiration + physical evaporation,
Therefore, diffuse radiation effect will depend on whether the
landscape is transpiration dominated or evaporation dominated
(and is discussed ahead).
Why is there no consistent relation between AOD and LHF?
LHF-Diffuse Radiation relation
[LAI = leaf area index = total leaf area / surface area]
Latent heat flux = evaporation + transpiration
Evaporation is a function of temperature (due to direct radiation);
Transpiration is directly dependent on plant photosynthesis and indirect
radiation.
Leaf Area Changes over the Life of the Plant
Determination of high and low
Leaf Area Index:
BV LAI 1998
7
High LAI –
6
Leaf Area Index > 3
5
Low LAI –
Leaf Area Index < 2.5
LAI
4
3
2
1
0
-1
140
160
180
200
220
240
260
280
Julian day
LAI change over Bondville AmeriFlux site
Working Hypothesis
At high vegetation LAI (leaf area index):
LHF is mainly due to transpiration;
with increasing aerosols,diffuse radiation
increases
this would cause increase the transpiration and
thereby increase LHF
At low vegetation LAI:
LHF is mainly due to evaporation;
with increasing aerosols,diffuse radiation
increases,
this would reduce the evaporation and therefore
LHF decreases.
Clustering for LAI Changes
Walker Branch (Forest site):
May 2001
June - Aug 1998
400.00
350.00
250.00
avg LHF
avg LHF
300.00
200.00
150.00
100.00
50.00
0.00
0.00
0.10
0.20
0.30
0.40
0.50
0.60
0.70
AOD 500nm
500
450
400
350
300
250
200
150
100
50
0
0
0.2
0.4
0.6
0.8
AOD 500nm
Low LAI case (LAI < 2.5)
High LAI case (LAI >3)
LHF decrease with aerosol loading
LHF increase with aerosol loading
1
However, analyzed results vary for different
landscapes
Bondville (soy bean site(C3)):
BV June-Aug 1998
400
320
350
Latent Heat Flux (W/m2)
Latent Heat Flux (W/m2)
BV June-Aug 1998
340
300
280
260
240
220
300
250
200
150
200
180
0.1
0.2
0.3
0.4
0.5
Aerosol Optical Depth
Low LAI case
0.6
100
0.1
0.2
0.3
0.4
0.5
0.6
Aerosol Optical Depth
High LAI case
0.7
0.8
Effect of Temperature changes:
With AOD changes, as a result of radiation
changes, air temperature can also change
(warming or cooling depending on aerosol type)
BV 1999
BV 1998
34
35
32
30
Air Temperature
Air Temperature
30
28
26
24
25
20
15
22
20
0
0.2
0.4
0.6
0.8
Aerosol Optical Depth
Corn
1
1.2
10
0
0.2
0.4
0.6
0.8
Aerosol Optical Depth
Soybean
1
AOD-LHF relation after accounting for both
leaf area and air temperature effects:
BV June-Aug 1999
BV June-Aug 1998
3
8
LHF/LAI/Air Temperature
LHF/LAI/Air Temperature
7
2.5
2
1.5
1
6
5
4
3
2
1
0.5
0
0
0.1
0.2
0.3
0.4
0.5
0.6
Aerosol Optical Depth
corn site
0.7
0.8
0
0.2
0.4
0.6
0.8
Aerosol Optical Depth
soy bean site
More consistent LHF decrease with increasing aerosol loading
1
AOD - LHF-vpd - Albedo nexus
(soybean)
Bondville 2001
0.24
0.23
Bondville 1999
0.21
3
0.2
2.5
0.19
0.18
0.17
0
0.2
0.4
0.6
0.8
Aerosol Optical Depth
1
Vapor Pressure Deficit
Albedo
0.22
2
1.5
1
0.5
0
0
0.2
0.4
0.6
0.8
Aerosol Optical Depth
1
1.2
Conclusions:
Aerosols affect land surface processes

Results confirmed for different canopy conditions (mixed forests,
corns, soybeans, winter wheat and grasslands).
CO2 sink increases with increasing aerosol loading over
forests and croplands (both C3 and C4)
CO2 source increases with increasing aerosol loading
over grasslands
Water Vapor Flux generally decreases with increasing
aerosol loading

Exceptions were winter wheat sites,one grassland, and high LAI
forest sites
Ongoing and Future work:
Isolating the effects of different
variables in understanding the
aerosol feedbacks on the land
surface response
Initial work with offline model
(GEMTM)
Followed by coupled model
(with RAMS)
What could the results yield?
-Generate defensible and testable results
considering feedbacks
-Incorporate LCLUC as a critical driver for
climate change forcing in a hydrological
framework (beyond current “temperaturecentric” feedback)
- Scaling (time and space based) still remains
the biggest disconnect and the multisensor –
calibration / model algorithm mapping will be
an approach
Additional references
Direct Observations of the Effect of Aerosol Loading on Net Ecosystem CO2
Exchange over different landscapes, Geophys. Res. Lett., Published
October 2004 (Niyogi et al.)
Direct Observations of the Aerosols Effects on Terrestrial Carbon and Water
Cycles, AGU Fall Meeting, Dec 2004 (Niyogi et al.)
NASA Press Release (UPN, Yahoo News,Washington Post, and over 50
other sites) [NASA study finds tiny particles in air may affect carbon sinks;
Dec 16, 2004]
http://www1.nasa.gov/vision/earth/environment/aerosol_carbon.html
Direct Observations of the Effect of Aerosols on Water Cycles, in
preparation (Early 2005 submission)
Thanks!